The purification and filtration of water and other aqueous solutions is necessary for many applications such as the provision of safe portable drinking water, the treatment of feeds, process streams and by-products associated with various industrial processes, and the treatment and handling of municipal waste water. Known methods for purifying aqueous solutions include reverse osmosis, distillation, ion-exchange, chemical adsorption, coagulation, flocculation, and filtering or retention. Many of these purification practices can be costly, energy inefficient and require significant technical know-how and sophistication to implement on both large and small scales. As a result, many advanced fluid purification technologies have had limited application beyond municipal or industrial applications.
Biological contaminants such as bacteria and fungi can be removed from aqueous solutions through ultrafiltration, but viruses are generally too small for filtration to be an effective means of purification. Because filtration is only somewhat effective, treatment with chemical additives tends to be the method of choice to address the presence of such contaminants. Examples of chemical additives include strong oxidizing agents such as chlorine, hydrogen peroxide, ozone or quaternary amine salts, flocculating agents, and precipitation agents. However, the use of chemical additive(s) requires careful administration and monitoring of the treated solutions as well special handling, transport, and storage, rendering them more costly and less desirable for many applications. As a result, simplified means for removing biological contaminants from aqueous solutions is desired.
In addition, with the recent rise in terrorism, governments around the world have become increasingly concerned about the effects of chemical warfare agents, biological agents, industrial chemicals and other toxic materials. Because nations stockpile such materials for both industrial uses and for use as warfare agents, such contaminants represent a hazard to armed forces and civilian populations due to potential exposure through inhalation, absorption, and/or ingestion. As a result, the contamination of ground water and other sources of portable water with chemical and biological contaminants is a primary concern for the military and for municipal governments and utility districts.
Commonly known chemical warfare agents include organosulfur-based compounds such as 2,2′-Dichlorodiethyl sulfide (HD, mustard, mustard gas, S mustard or sulfur mustard), which are known as “blister” or “blistering” agents and can be lethal in high doses. Other chemical warfare agents include organophosphorus-based (“OP”) compounds, such as O-ethyl S-(2-diisopropylamino) ethyl methylphosphonothiolate (VX), 2-Propyl methylphosphonofluoridate (GB or Sarin), and 3,3′-Dimethyl-2-butyl methylphosphonofluoridate (GD or Soman), which are commonly referred to as “nerve” agents because they attack the central nervous system and can cause paralysis and potentially death in a short period of time. Other chemical contaminants include certain industrial chemicals, insecticides and pesticides such as parathion, paraoxon and malathion, which can also have harmful effects.
Methods and materials for decontaminating surfaces exposed to chemical warfare agents are known in the art. Yang et al., “Decontamination of Chemical Warfare Agents”, Chem. Rev. Vol. 92, pp 1729-1743 (1992). These methods and materials tend to function by chemically reacting with and/or adsorbing the chemical warfare agent, but are focused on decontaminating vehicles, equipment, personnel and other surfaces that have been exposed to the agent. Because such methods and materials are not suitable or sufficiently effective at treating chemical warfare agents in solution there remains a need for simplified means for removing and/or detoxifying a broad spectrum of chemical contaminants from aqueous solutions, including, but not limited to, nerve agents, blister agents, pesticides, insecticides and other toxic chemical agents.
Moreover, exposure to chemical and biological contaminants through inhalation is also a concern that has not been adequately addressed. Basic methods that are used to control air quality include filtration, absorption on solid sorbents, electrostatic precipitation, chemical conversion, and treatment with various forms of radiation including heat, ultraviolet light and microwave. Gas filtration methods tend to be limited by the pore size of the filters, and are generally not capable of removing many biological and chemical contaminants. The use of ultra small pore sizes tend to clog due to particulates on the filter producing excessive pressure drop across the filter that is unacceptable for many applications. Electrostatic precipitation operates by imposing a charge on particles and then removing them from a gas stream onto an oppositely charged surface such as on a collection plate. This technique is not well suited for high velocity gas streams, for fluids containing volatile chemical contaminants or for contaminants that are otherwise difficult to charge. Chemical reactions tend to be effective on only small volumes of gas and can require additional processing or handling of the gas to remove undesirable and potentially harmful reagents and byproducts that remain. Heating, although effective for removing many types of biological and chemical contaminants from gases, tends to be ineffective on higher velocity gas streams. Ultraviolet light can be effective but is difficult to implement on larger gas volumes as the light tends to be absorbed by only those contaminants in the portion of the gas stream immediately adjacent the light source.
Adsorption of gases on a sorbent can be effective particularly where the sorbent is specifically matched to the contaminant to be removed from the gas. However, where the specific nature of the contaminant is not known or where the gas stream contains a number of diverse contaminants the use of known sorbents may not adequately purify the gas. As a result, there remains a need for a composition that is capable of removing, deactivating and/or detoxifying a diverse set of biological and chemical contaminants such as bacteria, viruses, nerve agents, blister agents, pesticides insecticides and other toxic chemical agents that may be present in a variety of fluids, including both aqueous solutions and gases.